Sheet-like material

ABSTRACT

The present invention provide a sheet-like material having a highly soft texture, and further having high crease resistance while being soft. The sheet-like material of the present invention is a sheet-like material which includes a nonwoven fabric containing ultrafine fibers having an average single fiber diameter of 0.3 to 7 μm, and an elastomer, and having nap on a surface, in which the elastomer has a porous structure, and the porous structure has a proportion of micropores with a pore size of 0.1 to 20 μm of 60% or more in all pores.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Phase application of PCT/JP2017/046354, filedDec. 25, 2017, which claims priority to Japanese Patent Application No.2017-009507, filed Jan. 23, 2017, the disclosures of these applicationsbeing incorporated herein by reference in their entireties for allpurposes.

FIELD OF THE INVENTION

The present invention relates to a sheet-like material, particularly toa napped leather-like sheet-like material.

BACKGROUND OF THE INVENTION

It is widely known to obtain a suede-like or nubuck-like, nappedleather-like sheet-like material by buffing with sandpaper a surface ofa sheet-like material in which a base material such as a nonwoven fabriccomposed of fibers is impregnated with a polyurethane resin to stand thefibers. Desired properties of the napped leather-like sheet-likematerial can be arbitrarily and widely designed by combination of a basematerial composed of fibers and a polyurethane resin.

For example, it is proposed that when a polycarbonate-based polyurethaneresin is used which is obtained by a reaction of a polycarbonate polyolhaving a specific structure with an aromatic polyisocyanate, softness ofthe polycarbonate-based polyurethane resin is improved, grindabilityobtained by using sandpaper is improved whereby a preferable nap lengthof a ultrafine fiber is expressed, and an artificial leather having anelegant appearance, a supple surface touch and soft texture due to napcan be obtained (see Patent Document 1).

The napped leather-like sheet-like material has an appearance and asurface closely resembling to natural leather, and is recognized to haveadvantages which do not exist in the natural leather, such as uniformityand color fastness. Use of the napped leather-like sheet-like materialhas recently been spread to long-term uses such as covering materialsfor furniture such as sofa and seat covers for automobiles, in additionto clothing use. In the clothing use among them, artificial leatherhaving both excellent softness and crease resistance has been required.

According to the proposal described above, it is proposed that softartificial leather can be obtained by making a structure of thepolycarbonate polyol forming the polyurethane resin specific to thehardness of the polycarbonate-based polyurethane resin which is theconventional problem. In the use requiring the soft texture as in theclothing use, however, the softness has been still insufficient.

It is also proposed that when a polyurethane resin including a bio-basedpolycarbonate polyol is used, synthetic leather having excellentlow-temperature flexing and contributing to environmental loadingreduction can be obtained (see Patent Document 2). According to thisproposal, however, synthetic leather composed of layers of nonporouspolyurethane resins having various molecular weights and a fiber fabrichas been studied in detail, but napped artificial leather having a softtexture and crease resistance has not been studied at all.

A method for obtaining a suede-like, leather-like sheet whose color toneis not changed and which has an elegant appearance is proposed, thesheet being obtained in a manner in which a porous layer havingmicropores is formed by adding a specific coagulation modifier to apolyurethane resin and the layer is napped by grinding (see PatentDocument 3). According to this proposal, a good texture has beenattained by controlling pore sizes in layers of nonporous polyurethaneresins having various molecular weights, and in portions close to thesurface layer and the fibrous base layer, but coexistence of softnessand crease resistance has not been studied at all, and softness isimpaired because of porous polyurethane resin layer.

Separately, a method for obtaining a sheet-like material having nap andelegant appearance in a manner in which a polyurethane resin having goodgrindability is obtained by containing pores having a diameter of 10 to200 μm inside a water-dispersible polyurethane resin, and a sheetobtained therefrom is ground with sandpaper, or the like is proposed(see Patent Document 4). According to this proposal, however, when thepores inside the polyurethane resin layer have a large pore size of morethan 20 μm, the thickness of the polyurethane resin layer between thepores is thick, so that an effect of improving the grindability of thepolyurethane resin and an effect of improving softness areinsufficiently exhibited. Accordingly, it has been difficult to obtainsufficient softness in the use requiring flexible deformation along acomplicated shape such as in clothing use. It has been also difficult toobtain ultrafine and uniform pores.

It is also proposed that a leather-like base material having lightweightand supple texture is obtained which is composed of a porous elastomerhaving a specific pore size and a nonwoven fabric of porous hollowfibers (see Patent Document 5). According to this proposal, the materialhas a soft texture because of the porous structure and is uniform, butit has been difficult to have both softness and crease resistance due toremaining creases.

As described above, it has been very difficult to stably obtain a nappedleather-like sheet-like material having both excellent softness andexcellent crease resistance according to the conventional techniques.

PATENT DOCUMENTS

-   Patent Document 1: WO2005/095706-   Patent Document 2: Japanese Patent Laid-open Publication No.    2014-1475-   Patent Document 3: Japanese Patent Laid-open Publication No.    2000-303368-   Patent Document 4: Japanese Patent Laid-open Publication No.    2011-214210-   Patent Document 5: Japanese Patent Laid-open Publication No.    2012-214944

SUMMARY OF THE INVENTION

In view of the background of the prior art described above, an object ofthe present invention is to provide a napped leather-like sheet-likematerial having both a texture of excellent softness and high creaseresistance while it is soft.

The present invention is to solve the problems described above, and thesheet-like material of the present invention is a sheet-like materialcomprising a nonwoven fabric containing ultrafine fibers having anaverage single fiber diameter of 0.3 to 7 μm, and an elastomer, andhaving nap on a surface, wherein the elastomer has a porous structure,and the porous structure has a proportion of micropores with a pore sizeof 0.1 to 20 μm of 60% or more in all pores.

According to a preferable embodiment of the sheet-like material of thepresent invention, the elastomer exists in an interior space in thenonwoven fabric.

According to a preferable embodiment of the sheet-like material of thepresent invention, the elastomer is a polycarbonate-based polyurethaneresin.

According to a preferable embodiment of the sheet-like material of thepresent invention, the polyurethane resin has a weight-average molecularweight of 30,000 to 150,000.

According to a preferable embodiment of the sheet-like material of thepresent invention, a number of pores per unit area in section is 50pores/1600 μm² or more in the porous structure in the elastomer.

According to the present invention, a napped leather-like sheet-likematerial having both a highly soft texture and crease resistance can beobtained. Specifically, a napped leather-like sheet-like material havingan elegant appearance obtained by buffing, and further having excellentsoftness and crease resistance can be obtained by the present invention.Here, the term “highly soft texture” means, in clothing use, that thesheet-like material can be tailored into a complicated three-dimensionalshape and can provide good feeling of wearing by deformation along withthe physical movement, and means, in use of furniture, automobileinterior materials, or the like, that the sheet-like material can bemolded or processed along with a complicated three-dimensional shape andcan provide good feeling of use by flexibly following deformationcaused, for example, when a person sits. The term “crease resistance”refers to an excellent recovery from the crease, and means that even ifwrinkles are caused by applying a load, for example, a deformationcaused upon the use as described above, the wrinkles disappear withoutleaving any trace after removing the load. It is necessary to applyappropriate elasticity to the sheet-like material in order to expressthe crease resistance, which is conflict with the softness, and thus ithas been difficult to obtain both the softness and the creaseresistance.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The sheet-like material of the present invention is a sheet-likematerial comprising a nonwoven fabric containing an ultrafine fibershaving an average single fiber diameter of 0.3 to 7 μm, and anelastomer, and having nap on a surface, in which the elastomer has aporous structure, and the porous structure has a proportion ofmicropores with a pore size of 0.1 to 20 μm of 60% or more in all pores.

The sheet-like material of the present invention comprises, as describedabove, a nonwoven fabric containing ultrafine fiber, and an elastomer.

As a material of the ultrafine fiber forming the nonwoven fabric used inthe present invention, it is possible to use thermoplastic resinscapable of melt-spinning, for example, polyesters such as polyethyleneterephthalate, polybutylene terephthalate, and polytrimethyleneterephthalate, polyamides such as 6-nylon and 66-nylon, and the like. Ofthese, a polyester is preferably used from the viewpoint of thestrength, dimensional stability, and light resistance. The nonwovenfabric may be mixed with ultrafine fibers of different other materials.

The cross-sectional shape of a single fiber forming the nonwoven fabricmay have a circular cross-section, and may be an elliptical, plane, orpolygonal such as triangle shape. A single fiber having a modifiedcross-section such as a sector or cruciform may also be used.

It is important that the ultrafine fibers that form the non-woven fabrichave an average single fiber diameter of 7 μm or less from the viewpointof the softness and nap appearance of the sheet-like material. Theaverage single fiber diameter is preferably 6 μm or less, and morepreferably 5 μm or less. On the other hand, it is important that theaverage single fiber diameter is 0.3 μm or more from the viewpoint ofthe chromogenic property after dying, the dispersibility of fiberbundles during buffing, and the easy handling. The average single fiberdiameter is preferably 0.7 μm or more, and more preferably 1 μm or more.

The average single fiber diameter herein refers to a value obtained bycutting the obtained sheet-like material in a thickness direction,observing a cross-section with a scanning electron microscope (SEM),measuring a fiber diameter of 50 arbitrary ultrafine fibers at threepoints, and calculating an average value of fiber diameters of a totalof 150 fibers.

As a method for obtaining the ultrafine fiber used in the presentinvention, use of an ultrafine fiber-generating fiber is a preferableembodiment. As the ultrafine fiber-generating fiber, anislands-in-the-sea fiber can be used in which two thermoplastic resincomponents having solubility in a solvent different from each other areused as a sea component and an island component, and the islandcomponent can be used as the ultrafine fiber by dissolving only the seacomponent in a solvent to be removed. A peelable composite fiber or amultilayered composite fiber can also be used in which two thermoplasticresin components are disposed alternately in a radial pattern of a fibercross-section or in a layer pattern, and each component is peeled anddivided to split the composite fiber into an ultrafine fiber.

As the nonwoven fabric, it is possible to use a nonwoven fabric in whichsingle fibers of the ultrafine fibers are entangled with one another,and a nonwoven fabric in which fiber bundles of the ultrafine fibers areentangled. However, the nonwoven fabric in which fiber bundles of theultrafine fibers are entangled is preferably used from the viewpoint ofthe strength and texture of the sheet-like material. A nonwoven fabrichaving appropriate voids between the ultrafine fibers inside the fiberbundle is particularly preferably used from the viewpoint of thesoftness and the texture. The nonwoven fabric in which fiber bundles ofthe ultrafine fibers are entangled, as described above, can be obtainedby previously entangling the ultrafine fiber-generating fibers and thengenerating the ultrafine fibers. The nonwoven fabric having appropriatevoids between the ultrafine fibers inside the fiber bundle can beobtained by using islands-in-the-sea fibers which can provideappropriate voids between the island components, i.e., between theultrafine fibers inside the fiber bundle, by removing the sea component.

As the nonwoven fabric, any of a staple fiber nonwoven fabric and afilament fiber nonwoven fabric can be used, and a staple fiber nonwovenfabric is preferably used from the viewpoint of the texture and theappearance.

A staple fiber in the staple fiber nonwoven fabric preferably has afiber length of 25 to 90 mm. When the fiber length is set to 25 mm ormore, the sheet-like material having the excellent abrasion resistancecan be obtained by entanglement. When the fiber length is set to 90 mmor less, the sheet-like material having a more excellent texture andappearance can be obtained. The fiber length is more preferably 35 to 80mm, and particularly preferably 40 to 70 mm.

When the ultrafine fibers or the fiber bundles thereof form the nonwovenfabric, a woven fabric or a knitted fabric may be inserted into thefabric in order to improve the strength. Fibers that form the wovenfabric or the knitted fabric used have preferably an average singlefiber diameter of about 0.3 to 10 μm.

The elastomer used in the present invention has a porous structure, anda proportion of micropores with a pore size of 0.1 to 20 μm in all poresin the porous structure is 60% or more. The ratio of the micropores ismore preferably 70% or more, and still more preferably 80% or more. Theporous structure may have either open cells or closed cells. When theelastomer has a certain ratio or more of the micropores, the softness ofthe elastomer can be increased, and the sheet-like material having ahighly soft texture can be obtained. In order to make the elastomer havethe porous structure having micropores, it is preferable to use wetcoagulation described below as a method for fixing the elastomer in thenonwoven fabric.

Further, by making the elastomer have the porous structure havingmicropores, a deformation force can be dispersedly received by not apart of the elastomer but by the whole elastomer when a creasedeformation is applied to the sheet-like material. Accordingly, thegeneration of the creases with buckling of the elastomer is suppressed,and the sheet-like material having the excellent crease resistance canbe obtained.

It is important that 60% or more of the pores with respect to all poresin the porous structure of the elastomer have a pore size of 0.1 μm ormore. The pore size is preferably 0.5 μm or more, and more preferably 1μm or more. When the pore size is set to 0.1 μm or more, the softness ofthe elastomer is increased and, at the same time, the cushioning againstthe deformation can be increased. On the other hand, it is alsoimportant that 60% or more of the pores with respect to all pores in theporous structure of the elastomer have a pore size of 20 μm or less. Thepore size is preferably 15 μm or less, and more preferably 10 μm orless. When the pore size is set to 20 μm or less, the pore density ofthe porous structure can be increased, both the softness and theappropriate strength can be obtained, and a deformation force can bedispersedly received by the whole elastomer, so that the sheet-likematerial having the excellent softness and the crease resistance can beobtained.

The number of pores per unit area in the porous structure of theelastomer is 50 pores/1600 μm² or more, preferably 70 pores/1600 μm² ormore, and more preferably 100 pores/1600 μm² or more. On the other hand,the number of pores per unit area in the porous structure of theelastomer is preferably 1000 pores/1600 μm² or less, and more preferably800 pores/1600 μm² or less.

When the number of pores per unit area is set to 50 pores/1600 μm² ormore, the porous structure having a soft texture is obtained and acrease deformation force of the sheet can be received by a plurality ofpores. Accordingly, the excellent crease resistance can be obtained.When the number of pores per unit area is too small, the deformationforce is concentrated to specific pores to cause buckling, and thecrease recovery is poor. When the number of pores per unit area is toolarge, a deformation space of the pores is too small, the deformationforce cannot be dispersed, and the crease recovery is poor.

The elastomer used in the present invention holds the ultrafine fibersin the sheet-like material. It is a preferable embodiment that theelastomer exists in an interior space of the nonwoven fabric from theviewpoint of having nap on at least one surface of the sheet-likematerial.

As the elastomer used in the present invention, a polyurethane resin ispreferably used in the point of obtaining uniform micropores in thesheet-like material. As the polyurethane resin, a polyurethane resinobtained by a reaction of a polymer diol with an organic diisocyanate ispreferably used.

Examples of the polymer diol may include polycarbonate-based,polyester-based, polyether-based, silicone-based, and fluorine-basedpolymer diols, and copolymers of combinations of these may also be used.

A polycarbonate-based polymer diol is preferably used, because it canprovide the appropriate rigidity to the polyurethane resin, theexcellent softness can be exhibited by forming the porous structurehaving micropores, and the high crease resistance can be exhibitedwithout buckling of the polyurethane resin.

The polycarbonate-based diol can be produced by transesterification ofan alkylene glycol with a carbonic acid ester, or a reaction of phosgeneor chloroformic acid ester with an alkylene glycol, or the like.

Examples of the alkylene glycol include linear alkylene glycols such asethylene glycol, propylene glycol, 1,4-butane diol, 1,5-pentane diol,1,6-hexane diol, 1,9-nonane diol, and 1,10-decane diol, branchedalkylene glycols such as neopentyl glycol, 3-methyl-1,5-pentane diol,2,4-diethyl-1,5-pentane diol, and 2-methyl-1,8-octane diol, alicyclicdiols such as 1,4-cyclohexane diol, aromatic diols such as bisphenol A,glycerol, trimethylol propane, and pentaerythritol. Eitherpolycarbonate-based diols obtained from alkylene glycol alone, orcopolymerized polycarbonate-based diol obtained from two or more kindsof alkylene glycols may be used.

Examples of the polyester-based diol may include polyester diolsobtained by condensation of a polybasic acid with various low molecularweight polyols.

As the low molecular weight polyols, it is possible to use one or morekinds of polyols selected from, for example, ethylene glycol,1,2-propylene glycol, 1,3-propylene glycol, 1,3-butane diol, 1,4-butanediol, 2,2-dimethyl-1,3-propane diol, 1,6-hexane diol,3-methyl-1,5-pentane diol, 1,8-octane diol, diethylene glycol,triethylene glycol, dipropylene glycol, tripropylene glycol,cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol. As the lowmolecular weight polyols, it is possible to use an adduct in whichbisphenol A is added with various alkylene oxides.

Examples of the polybasic acid include one or more kinds of acidsselected from, for example, succinic acid, maleic acid, adipic acid,glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,dodecane dicarboxylic acid, phthalic acid, isophthalic acid,terephthalic acid, and hexahydroisophthalic acid.

Examples of the polyether-based diol may include polyethylene glycol,polypropylene glycol, polytetramethylene glycol, and copolymerized diolsobtained by combination of these.

The polymer diol preferably has a number-average molecular weight of 500to 5000. When the number-average molecular weight is set to 500 or more,and more preferably 1500 or more, it is possible to prevent the texturefrom being hardened. When the number-average molecular weight is set to5000 or less, and more preferably 4000 or less, the strength as thepolyurethane resin can be maintained.

Examples of the organic diisocyanate used in the synthesis of thepolyurethane resin may include aromatic diisocyanates such as4,4′-diphenylmethane diisocyanate, praraphenylene diisocyanate,1,5-naphthalene diisocyanate, paraxylene diisocyanate, and methylenediisocyanate, alicyclic diisocyanates such as 4,4′-dicyclohexylmethanediisocyanate and isophorone diisocyanate, and aliphatic diisocyanatessuch as 1,6-hexamethylene diisocyanate. Of these, aromaticdiisocyanates, particularly 4,4′-diphenylmethane diisocyanate, arepreferably used from the viewpoint of the strength and durability suchas heat resistance of the obtained polyurethane resin.

As a chain extender used in the synthesis of the polyurethane resin, itis possible to use organic diols, organic diamines, hydrazinederivatives, and the like.

Examples of the organic diol may include aliphatic diols such asethylene glycol, propylene glycol, 1,4-butane diol, neopentyl glycol,1,5-pentane diol, methylpentane diol, 1,6-hexane diol, 1,7-heptane diol,1,8-octane diol, 1,9-nonane diol, and 1,10-decane diol, alicyclic diolssuch as 1,4-cyclohexane diol and hydrogenated xylylene glycol, andaromatic diols such as xylene glycol.

Examples of the organic diamine may include ethylene diamine, isophoronediamine, xylene diamine, phenyl diamine, and 4,4′-diaminodiphenylmethane.

Examples of the hydrazine derivative may include hydrazine, adipic aciddihydrazide, and isophthalic acid dihydrazide.

In order to improve the water resistance, the abrasion resistance, andthe hydrolysis resistance, a cross-linking agent can be added to thepolyurethane resin. The cross-linking agent may be an externalcross-linking agent that is added to the polyurethane as a thirdcomponent, or an internal cross-linking agent can be used whichpreviously introduces a reaction point forming a cross-linked structureinto a polyurethane molecular structure.

In the synthesis of the polyurethane resin, it is possible to use, as acatalyst, amines such as triethyl amine and tetramethyl butane diamine,metal compounds such as potassium acetate, zinc stearate, and tinoctylate, and the like, for example.

The polyurethane resin used in the present invention preferably has aweight-average molecular weight (Mw) of 30,000 to 150,000, and morepreferably 50,000 to 130,000. When the weight-average molecular weight(Mw) is set to 30,000 or more, the strength of the obtained sheet-likematerial can be maintained, and the loss of nap and the occurrence ofpilling can be prevented. When the weight-average molecular weight (Mw)is set to 150,000 or less, the polyurethane resin in the sheet-likematerial can have uniform micropores. When the polyurethane resin hassuch a weight-average molecular weight (Mw) range, the uniform andultrafine porous structure can be obtained by the temporary softening ofthe polyurethane resin with heating and the evaporation of the solubleand insoluble solvents contained in the polyurethane resin after wetcoagulation described below as the starting point, in the productionsteps usually used where the polyurethane resin is fixed into thenonwoven fabric in the wet coagulation, and then the sheet-like materialcontaining a insoluble solvent such as water is dried with heating.

The elastomer may contain polyester-based, polyamide-based, andpolyolefin-based elastomers, acrylic resins, and ethylene-vinyl acetateresins within a range in which the performance and the texture are notimpaired. In addition, the elastomer may also contain various additives,for example, pigments such as carbon black, flame retardants such asphosphorus-based, halogen-based, and inorganic flame retardants,antioxidants such as phenol-based, sulfur-based, and phosphorus-basedantioxidants, UV absorbers such as benzotriazole-based,benzophenone-based, salicylate-based, cyanoacrylate-based, and oxalicacid anilide-based UV absorbers, light stabilizers such as hinderedamine-based and benzoate-based light stabilizers, hydrolysis stabilizersuch as polycarbodiimide, plasticizers, antistatic agents, surfactants,coagulation modifiers, dyes, and the like.

In the sheet-like material of the present invention, an amount of theelastomer in the sheet-like material is preferably 10 to 50% by mass,and more preferably 15 to 35% by mass. When the amount of the elastomeris set to 10% by mass or more, the sheet-like material obtains thestrength, and it is possible to prevent fiber falling. When the amountof the elastomer is set to 50% by mass or less, it is possible toprevent the texture from being hardened, and the desired good napappearance can be obtained.

Examples of the method of fixing the elastomer into the nonwoven fabricinclude methods in which the nonwoven fabric is impregnated with asolution of the elastomer, followed by wet coagulation or drycoagulation. The wet coagulation is preferably used from the viewpointof obtaining the uniform and ultrafine porous structure as in thepresent invention. As the solvent used when the polyurethane resin isgiven as the elastomer, N,N′-dimethyl formamide, dimethyl sulfoxide, andthe like may be used. Specifically, the nonwoven fabric is immersed in asolution in which the elastomer is dissolved in the solvent to give theelastomer to the nonwoven fabric, and is immersed in the insolublesolvent for the coagulation. It is also possible to perform thecoagulation by immersing the nonwoven fabric in a mixture of the solublesolvent and the insoluble solvent.

The sheet-like material of the present invention may also be obtained bydividing the material in half or into several sections in the thicknessdirection of the sheet-like material before buffing.

The addition of the antistatic agent before buffing is preferablyperformed, because grinded powder generated from the sheet-like materialby grinding tends to be hardly accumulated on the sandpaper.

The sheet-like material of the present invention is eventually usedsuitably as a napped leather-like sheet-like material in which ultrafinefibers are buffed on at least one surface of the sheet-like material.The buffing is performed by a method in which grinding is conductedusing sandpaper, a roll sander, or the like. In order to obtain goodfiber nap on the surface, it is a preferable embodiment that a lubricantsuch as a silicone emulsion is applied before the buffing.

The sheet-like material of the present invention is eventually usedsuitably as a napped leather-like sheet-like material in which ultrafinefibers are buffed on at least one surface of the sheet-like material.

The sheet-like material of the present invention can be suitably used ascovering materials used in furniture, chairs, wall covering, and seats,ceilings and interior finishing products in interior of vehicles such asautomobiles, trains and airplanes, and further covering materials havinga very elegant appearance of clothes.

EXAMPLES

The sheet-like material of the present invention is more specificallydescribed by way of Examples below.

[Evaluation Method] (1) Average Single Fiber Diameter:

A cross-section of a nonwoven fabric containing fibers of a sheet-likematerial, which was vertical to the thickness direction of the fabric,was observed at 3000 magnifications using a scanning electron microscope(SEM, VE-7800-type manufactured by Keyence Corporation), and diametersof 50 single fibers that were randomly extracted from a 30 μm×30 μmvisual field were measured at a unit of μm up to the first decimalplace. The measurement was performed at three points, diameters of 150single fibers in total were measured, and an average value up to thefirst decimal place was calculated. In the case where fibers having afiber diameter of more than 50 μm are present, it is considered thatthose fibers do not correspond to the ultrafine fibers, and they wereexcluded from objects to be measured for the average fiber diameter.When the ultrafine fiber had a modified cross-section, first, across-sectional area of a single fiber was measured, and supposing thatthe cross-section had a circle, the diameter was calculated to obtain adiameter of the single fiber. An average value was calculatedconsidering the values above as a population, which was defined as anaverage single fiber diameter.

(2) Pore Size of Porous Structure of Elastomer and Proportion ofMicropores with Pore Size of 0.1 to 20 μm in all Pores in PorousStructure:

A cross-section of a nonwoven fabric containing elastomers of asheet-like material, which was vertical to the thickness direction ofthe fabric, was observed at 2000 magnifications using a scanningelectron microscope (SEM, VE-7800-type manufactured by KeyenceCorporation), and pore sizes (diameter) of 50 pores in elastomers thatwere randomly extracted from a 40 μm×40 μm visual field were measured ata unit of μm up to the first decimal place. The measurement wasperformed at three points, pore sizes of 150 pores in total weremeasured, and the proportion of the number of pores with a pore size of0.1 to 20 μm in 150 pores was calculated, and the proportion was definedas the proportion of micropores with a pore size of 0.1 to 20 μm in theporous structure. When the pores in the elastomers were variant pores,first, a cross-sectional area of a pore was measured, and supposing thatthe cross-section had a circle, the diameter was calculated to obtain apore size (diameter) of the pore.

(3) The Number of Pores Per Unit Area in Porous Structure of Elastomer:

A cross-section of a nonwoven fabric containing elastomers of asheet-like material, which was vertical to the thickness direction ofthe fabric, was observed at 2000 magnifications using a scanningelectron microscope (SEM, VE-7800-type manufactured by KeyenceCorporation), and the number of pores in the elastomer was counted in a40 μm×40 μm visual field. The count was performed at three points, andan arithmetic average value of the number of pores was defined as thenumber of pores per unit area in the porous structure. When the area ofthe elastomer containing the porous structure is less than the 40 μm×40μm visual field, the number of pores in the visual field was divided byan effective area of the elastomer, and the obtained value was convertedinto the number of pores per 1600 μm², which was defined as the numberof pores per unit area in the porous structure. When the pore size ofthe pore is larger than the 40 μm×40 μm visual field, the number ofpores in the porous structure was defined as 1.

(4) Weight-Average Molecular Weight of Polyurethane Resin:

The polyurethane resin was extracted from the obtained sheet-likematerial using N,N′-dimethylformamide (hereinafter may sometimes bereferred to as “DMF”), the concentration of the polyurethane resin wasset to 1% by mass, and a weight-average molecular weight of thepolyurethane resin was measured by gel permeation chromatography (GPC)under the following conditions:

Apparatus: GPC measuring apparatus HLC-8020 (manufactured by Tosoh).

Column: TSK gel GMH-XL (manufactured by Tosoh)

Solvent: N,N-dimethylformamide (hereinafter referred to as “DMF”

Standard sample: polystyrene (TSK standard polystyrene manufactured byTosoh)

Temperature: 40° C.

Flow rate: 1.0 ml/minute

(5) Softness:

Five specimens each having a size of 2×15 cm (a vertical direction×ahorizontal direction) were made in accordance with the A method (450Cantilever Method) described in 8.21.1 in 8.21 “Bending Stiffness” inJIS L 1096:2010 “Testing Methods for Woven and Knitted Fabrics”. Each ofthe specimens was put on a horizontal table having a slope with an angleof 45°. The specimen was slid, and the scale was read when the centralpoint on one end of the specimen was brought into contact with theslope. An average value of the five specimens was obtained. When thevalue was 45 mm or less, the softness was evaluated as good.

(6) Crease Resistance:

Crease recovery angles for five specimens were measured using a 10 Nload apparatus in accordance with JIS L 1059-1:2009 “Testing Methods forCrease Recovery of Textiles—Part 1: Determination of the Recovery fromCreasing of a Horizontally Folded Specimen by Measuring the Angle ofRecovery (Monsant Method)”, the crease resistance was calculated by theformula of crease resistance ratio described in section 10 “Calculationof Crease Recovery Angle and Crease Resistance Ratio”, and an averagevalue of the five specimens was obtained. When the value was 90% ormore, the crease resistance was evaluated as good.

[Expression of Chemical Substance]

Abbreviations of chemical substances used in Examples and ComparativeExamples have the following meanings:

PU: polyurethane

DMF: N,N-dimethylformamide

Example 1

An islands-in-the-sea fiber including a polystyrene as a sea componentand a polyethylene terephthalate as an island component was drawn,crimped, and cut to obtain a raw stock for a nonwoven fabric.Subsequently, the obtained raw stock was formed into fiber webs using across-lapper, and needle punching was performed to obtain a nonwovenfabric.

The thus obtained nonwoven fabric composed of the islands-in-the-seafiber was impregnated with an aqueous solution of polyvinyl alcohol,dried, and then the polystyrene as the sea component was extracted intrichloroethylene to be removed. The resulting material was dried toobtain a nonwoven fabric composed of ultrafine fibers having an averagesingle fiber diameter of 2.0 μm.

The thus obtained nonwoven fabric composed of ultrafine fibers wasimmersed in a resin solution in which a concentration of a solution of apolycarbonate-based polyurethane resin in DMF was adjusted to 11%, andan adhesion amount of the polyurethane (PU) resin solution wascontrolled by using a squeeze roll. Then, the PU resin was coagulated inan aqueous solution having a DMF concentration of 30%, subsequently,polyvinyl alcohol and DMF were removed by hot water, and the resultingmaterial was dried to obtain a sheet-like material having a PU resincontent of 17% by mass. One side of the thus obtained sheet-likematerial was subjected to buffing using 180-mesh endless sandpaper, andthen was dyed with a dispersion dye to obtain a napped leather-likesheet-like material.

When a cross-section in the thickness direction of the inside of theobtained leather-like sheet-like material was observed with a scanningelectron microscope (SEM), it was found that the polyurethane resinexisted only in the inside of the nonwoven fabric, the polyurethaneresin had a porous structure having micropores, the proportion ofmicropores with a pore size of 0.1 to 20 μm in all pores in the porousstructure was 85%, and the number of pores per unit area in the porousstructure was 247 pores/1600 μm². The polyurethane resin extracted fromthe napped leather-like sheet-like material had a weight-averagemolecular weight of 110,000.

The obtained napped leather-like sheet-like material had a good naplength and dispersibility of the fibers, and had the excellent softnessand the crease resistance. The results are shown in Table 1.

Examples 2 to 7 and Comparative Examples 1 to 5

A napped leather-like sheet-like material was manufactured in the samemanner as in Example 1, except that the average single fiber diameter ofthe ultrafine fiber, the kind of the polyurethane resin, and theweight-average molecular weight of the polyurethane resin were changedto values shown in Table 1.

When a cross-section in the thickness direction of the inside of theleather-like sheet-like material in each of Examples and ComparativeExamples was observed with a scanning electron microscope (SEM), it wasfound that the polyurethane resin had a porous structure havingmicropores, and the polyurethane resin existed only in the inside of thenonwoven fabric.

Table 1 shows the average single fiber diameter of the ultrafine fiber,the kind of the polyurethane resin, the weight-average molecular weightof the polyurethane resin, the average particle size of the porousstructure of the polyurethane in the obtained sheet-like material, theproportion of micropores with a pore size of 0.1 to 20 μm in all poresin the porous structure, the softness, and the crease resistance in eachExample and each Comparative Example.

TABLE 1 Average pore Proportion of Weight-average size of microporeswith Number of pores per Average single Kind of molecular weight porouspore size of 0.1 unit area in porous Crease fiber diameter polyurethaneof polyurethane structure to 20 μm in pore structure Softness resistance(μm) resin resin (μm) structure (%) (pores/1600 μm) (mm) (%) Example 12.0 polycarbonate-based 110,000 3.3 85 247 35 96 Example 2 2.0polycarbonate-based 70,000 7.2 71 92 31 91 Example 3 2.0polycarbonate-based 140,000 14.5 63 53 43 90 Example 4 4.4polycarbonate-based 110,000 3.1 81 252 41 94 Example 5 5.5polycarbonate-based 110,000 3.2 83 245 42 93 Example 6 2.0polyether-based 110,000 8.5 68 76 30 90 Example 7 2.0 polyester-based110,000 4.7 74 160 32 91 Comparative 2.0 polycarbonate-based 160,00019.4 52 12 50 86 Example 1 Comparative 2.0 polycarbonate-based 200,00038.0 30 1 54 82 Example 2 Comparative 2.0 polycarbonate-based 260,00071.8 14 1 57 80 Example 3 Comparative 2.0 polyether-based 200,000 58.719 1 48 78 Example 4 Comparative 2.0 polyester-based 200,000 41.3 26 152 80 Example 5

In all of the napped leather-like sheet-like materials in Examples 1 to7, the polyurethane resin had the porous structure having micropores,and both the excellent softness and the excellent crease resistance wereobtained by adjusting the weight-average molecular weight of thepolyurethane resin, the average pore size of the pores in the porousstructure, the proportion of micropores with a pore size of 0.1 to 20 μmin all pores in the porous structure, and the number of pores per unitarea in the porous structure. On the other hand, in the sheet-likematerials in Comparative Examples 1 to 5, the porous structure wasformed in the polyurethane resin by the increase of the weight-averagemolecular weight of the polyurethane resin, but the pores were large andununiform, and the thickness of the polyurethane resin between the poresbecame thick, thus resulting in the reduced softness. Also the pore sizewas not uniform, and thus the crease deformation could not be receivedby the whole polyurethane resin, thus resulting in the poor creaseresistance.

1. A sheet-like material comprising a nonwoven fabric containingultrafine fibers having an average single fiber diameter of 0.3 to 7 μm,and an elastomer, and having nap on a surface, wherein the elastomer hasa porous structure, and the porous structure has a proportion ofmicropores with a pore size of 0.1 to 20 μm of 60% or more in all pores.2. The sheet-like material according to claim 1, wherein the elastomerexists in an interior space in the nonwoven fabric.
 3. The sheet-likematerial according to claim 1, wherein the elastomer is apolycarbonate-based polyurethane resin.
 4. The sheet-like materialaccording to claim 3, wherein the polyurethane resin has aweight-average molecular weight of 30,000 to 150,000.
 5. The sheet-likematerial according to claim 2, wherein the elastomer is apolycarbonate-based polyurethane resin
 6. The sheet-like materialaccording to claim 5, wherein the polyurethane resin has aweight-average molecular weight of 30,000 to 150,000.
 7. The sheet-likematerial according to claim 1, wherein a number of pores per unit areain section is 50 pores/1600 μm² or more in the porous structure in theelastomer.
 8. The sheet-like material according to claim 2, wherein anumber of pores per unit area in section is 50 pores/1600 μm² or more inthe porous structure in the elastomer.
 9. The sheet-like materialaccording to claim 3, wherein a number of pores per unit area in sectionis 50 pores/1600 μm² or more in the porous structure in the elastomer.10. The sheet-like material according to claim 4, wherein a number ofpores per unit area in section is 50 pores/1600 μm² or more in theporous structure in the elastomer.
 11. The sheet-like material accordingto claim 5, wherein a number of pores per unit area in section is 50pores/1600 μm² or more in the porous structure in the elastomer.
 12. Thesheet-like material according to claim 6, wherein a number of pores perunit area in section is 50 pores/1600 μm² or more in the porousstructure in the elastomer.